1. The Field of the Invention
The present invention relates to systems and methods for implementing a novel retort heating apparatus. Specifically, the present invention relates to systems and processes for producing hydrocarbon gases and liquids and other by-products from solid matter, particularly from oil shale using a retort heating apparatus.
2. The Relevant Technology
Oil consumption in the United States has been estimated to be about 20 million barrels/day. In contrast, the U.S. domestic production of oil is estimated to be about 6 million barrel/day. This imbalance between consumption and demand on the one hand, and production on the other hand, emphasizes the need for continued development in the field of alternative fuel source technology. In addition, domestic resources should be explored rather than depending on foreign oil sources. For example, national parks and other recreation areas contain rich fuel recourses, the extent of which have yet to be fully tapped. The need for continued research and development in this area is enhanced by threats to oil supply and dependence on foreign oil supplies. Furthermore, oil deposits in the U.S. are either rare or protected by law. Thus, alternatives to conventional drilling are required.
However, conventional non-drilling oil extraction processes are not cost-effective compared to conventional drilling extraction processes. Technological solutions and new methods and processes for non-drilling extraction are therefore needed. Furthermore, it would be advantageous if these novel processes and systems permitted, in contrast with conventional extractive processes, the extraction of oil and the recovery of other products that are present in the feed material, such as mineral and nitrogen compounds.
The Green River oil shale formation that extends over eastern Utah, western Colorado, and a tip of southern Wyoming, is estimated to contain over one trillion barrels of recoverable oil, which makes of this formation the richest oil formation in the world. In theory, this formation could provide a world-wide supply of oil for about 150 years. In other words, the amount of oil in the Green River shale formation has been estimated to exceed the combined amounts of oil in known oil reserves in the entire world and of oil discovered so far. Other oil shale deposits are known to exist in the U.S. and also in other countries worldwide.
Oil shale contains a rich hydrocarbon source known as kerogen. Kerogen can be broken down into oil vapors and organic liquids by retorting processes. Retorting is a process by which kerogen is decomposed into derivatives such as oil, gas and other compounds. Retorting is also known as destructive distillation, which is the decomposition of kerogen by heat in a closed container and collection of the volatile products produced.
A number of fluid bed retorts have been developed. Generally, each of these systems allows crushed feed material to flow downward by gravity through a heated column as oil vapor is drawn off the column. Although most conventional retorts function to convert oil shale to oil, conventional systems have such poor efficiency that they are not economical to operate. Furthermore, many conventional systems have systemic problems that preclude their continued operation without shutting down and cleaning out the retort chamber.
For example, many conventional retorts operate by passing a hot gas up through crushed oil shale. To enable the hot gas to pass around the oil shale, the oil shale must be provided in relatively large particles. Such systems, however, have low production efficiency in that it is difficult to sufficiently heat the center of the large particles and it is difficult for the oil vapors to escape from the center of such particles. In addition, because the particles stay substantially stagnate relative to the surrounding particles as the hot air passes over them, the particles have a tendency to agglomerate or fuse together, thereby further decreasing the efficiency of oil vapor extraction. Such agglomerations can also block the flow of the material through the retort. Heated gases are also dangerous to work with in that they can be highly explosive and require extra measures to ensure that the gas is not leaked out of the retort.
In an alternative approach to using the free flow of heated gas, conduits have been provided within a retort. The conduits are heated by passing a heated gas therethrough. As the particles pass by the conduits, the particles are heated so as to emit the oil vapor. The primary problem with this approach is that the conduits do not uniformly heat the particles. For example, some particles pass through the retort without ever contacting the conduits. Other particles become stacked on top of the conduits preventing their passage through the retort. As a result of the lack of uniform heating, there are again problems with the formation of agglomerates and with low efficiency of oil vapor extraction.
In some conventional retorts, the oil vapor product is drawn out of the retort at the top of the column at substantially the same place where feed material is supplied. Because the temperature is generally cooler at the top of the retort than at the bottom, this allows the some oil vapors to cool and condense. During condensing of the oil vapors, the oil vapors may mix with some of the feed material, forming clumps of feed material which plug the fluid bed.